1. Field of the Invention
The invention relates to a method for mounting a harness on a seam weaving machine, an apparatus for making a flat woven fabric endless by means of a woven seam joining together opposite ends of the fabric and a harness carriage for use in the harness mounting method. Forming fabrics used in the wet end section of papermaking machines have to be made endless by a woven seam. The weave pattern is continued exactly in the woven seam so that the joining does not cause markings in the paper.
2. Related Prior Art
U.S. Pat. No. 4,581,794 and U.S. Pat. No. 4,557,025 disclose an automatic seaming machine for forming a seam in a length of woven fabric for joining opposite ends of the fabric together thereby to form an endless woven fabric belt. When using that machine, a strip of woven material, cut from one of the ends of the fabric, the so-called seam strip, is supported between the opposite ends of the fabric. The seam strip is clamped at one end and weights or springs are attached to the opposite end of this seam strip so that it is pulled taut. The warp threads are removed from the seam strip located between the opposite ends of the fabric leaving only the weft threads. The weft threads of the seam strip are drawn in through a shedding mechanism and are controlled by means of a Jacquard machine to form a shed opening. The opposite ends of the fabric each include a fringe formed by removing a majority of the weft threads within an end portion of approx. 20 cm. A few weft threads are left at the edge of the fringe to form a narrow lease functioning to maintain the warp threads of the fringe in the proper position and sequence and to maintain proper relative alignment of the warp threads with respect to each other. The woven seam is formed by separating a first one of the warp threads of the lease and drawing it through the shed opening formed by the weft threads of the seam strip. The shed is then changed and a warp thread drawn out of the lease at the opposite end of the strip is separated and woven into the weft threads of the seam strip. This cycle is repeated until a seam has been woven along the entire width of the fabric. The warp thread fringes and seam strip weft threads reproduce within the woven seam exactly the weave pattern of the fabric because the fabric has been thermoset after weaving so that the warp and weft threads of the fabric, which are synthetic monofilaments, are permanently crimped. The warp thread fringes and the seam strip weft threads will be forced by their thermoset crimp knuckles to cross each other exactly as in the fabric.
The automatic seam weaving machine comprises a Jacquard machine carriage which supports the Jacquard machine and the shedding mechanism including the heddling assembly and the spring box. A plurality of eyeletted heddles are mounted between the springs of the spring box and the vertically reciprocal hooks of the Jacquard machine. The heddles are designed such that they can be slidably placed over the weft threads so that the individual weft threads do not have to be threaded through the heddles. The heddling assembly is fixedly mounted on the Jacquard machine.
U.S. Pat. No. 5,386,854 discloses a seam weaving machine wherein the Jacquard machine is arranged slightly offset underneath the shedding mechanism, a plurality of harness cords extending vertically downward from the jacquard machine and being deflected by 180xc2x0 prior to passage through the shedding mechanism to return springs secured in the machine above the shedding mechanism.
U.S. Pat. No. 4,862,566 discloses an auxiliary device for a seam weaving machine. The auxiliary device couples each seam strip weft thread drawn in through one of the heddles to a tensioning string of a tensioning device. Said auxiliary device simplifies the drawing in of the seam strip weft threads through the heddles of the shedding mechanism.
U.S. Pat. No. 5,791,382 discloses a separable collar or coupling for the harness of the Jacquard machine. The separable collar enables a simple and quick connection and disconnection of a twine to one or several harness cords which in turn are fastened to the eyeletted heddles.
U.S. Pat. No. 5,636,663 discloses a harness system for weaving looms wherein all twines are releasably connected to one or several harness cords by means of couplings. The harness cords pass through openings in a plate which is reciprocally moveable so as to connect or disconnect all of the couplings simultaneously. In this way, the Jacquard machine can be disconnected from and reconnected to the shedding mechanism without the need to disconnect and connect each twine individually from the harness cords. A similar device for disconnecting and connecting a plurality of twines to harness cords collectively and simultaneously is disclosed in German Patent DE 42 13 958.
The width of the heddling assembly and the number of heddles or eyelets are fixed so that only small variations in the width of a woven seam and the density of the weft threads are possible with a specific heddling assembly. Each seam weaving machine can, therefore, be used only for fabrics within a narrow range of weave parameters. If a rather coarse fabric has to be made endless following a fine fabric on the same machine, the shedding mechanism has to be disconnected from the Jacquard machine and replaced by a shedding mechanism adapted to the coarser fabric. Such conversion of a seam weaving machine requires several days because each twine has to be disconnected from the harness cords of the previous shedding mechanism and reconnected to the harness cords of the new shedding mechanism separately.
Even if a fabric having the same parameters as the previous one has to be made endless, a standstill of several hours occurs because a new harness has to be drawn in, i.e. a new set of the seam strip weft threads has to be drawn in, through the eyeletted heddles or the eyelets. A Jacquard machine as used for a seam weaving machine includes, for example, 896 cords. Depending on the complexity of the weave pattern, it takes about 2 to 8 hours to draw in a new harness. A typical forming fabric for use in the wet end section of a papermaking machine has an average width of 7 meters. The opposite ends of such a fabric can be made endless by means of a seam weaving machine within about 10 to 15 hours. A standstill of several hours is, therefore, a considerable economic factor.
The weft threads of the seam strip cut from the fabric are arranged to form a shed opening so that they are used as or function as the warp thread in the seam weaving machine. Similarly, the warp thread fringes are drawn in through the shed opening so that they are used as or function as the weft threads in the seam weaving machine. The designations xe2x80x9cweft threadsxe2x80x9d and xe2x80x9cwarp threadsxe2x80x9d are used here in accordance with the arrangement the threads had in the fabric rather than in accordance with their function in the seam weaving machine.
The present invention provides a technique for adapting the design of a seam weaving machine quickly and without extended standstill periods of the seam weaving machine to the weave pattern and parameters of different fabrics. The improvement includes preparing the harness for a fabric having parameters differing from those of the previous fabric while the shedding mechanism is removed from the seam weaving machine and mounting the prepared shedding mechanism on the seam weaving machine, the twines and harness cords being coupled collectively.
Thus, in one aspect, the present invention provides a method for mounting a new harness on a seam weaving machine for making endless a flat woven fabric formed by interwoven warp and weft threads by means of a woven seam joining together opposite ends of the fabric, the opposite ends of the fabric each including a fringe of warp threads, the warp threads of the fringe being supported such that they can be interwoven with weft threads taken out of the fabric and drawn in through a shedding mechanism controlled by a Jacquard machine by means of twines and harness cords so that the weft threads drawn in form a shed opening, each of the harness cords being passed through one of a number of openings in a first plate, the harness cords being connected to the twines by means of couplings, each of the twines passing through one of a number of openings in a second plate, each coupling comprising a first and a second coupling element, each of the first coupling elements being fastened to a number of the harness cords and each of the second coupling elements being fastened to a twine, the first and second coupling elements being connectable by movement to a first position relative to each other and are disconnectable by movement to a second position relative to each other; the method comprising the steps of:
providing a harness carriage including first means for releasably supporting the shedding mechanism and second means for releasably supporting the first plate;
installing the shedding mechanism on the first supporting means;
installing the first plate on the second supporting means;
transferring the first plate from the second supporting means to the seam weaving machine and moving the first plate to the second plate so that all couplings will be moved together into the first positions so that the harness cords extending from the shedding mechanism are connected to the twines extending from the Jacquard machine; and
releasing the shedding mechanism from the first supporting means of the harness carriage and fastening the shedding mechanism to the seam weaving machine.
Preferably, the seam strip weft threads are to be drawn in through the shedding mechanism while the shedding mechanism is detached from the seam weaving machine and is attached to the harness carriage. Another shedding mechanism can be mounted on the seam weaving machine in order to make a fabric endless in the meantime.
In another aspect, the present invention provides an apparatus for making endless a flat woven fabric formed by interwoven warp and weft threads by means of a woven seam joining together opposite ends of the fabric. The apparatus comprises:
a shedding mechanism suitable for the weft threads taken out of the fabric being drawn in through the shedding mechanism, the shedding mechanism being controllable by harness cords to form a shed opening with the drawn in weft threads, into which shed opening the warp threads of the fringe can be drawn through for interweaving with the weft threads;
a Jacquard machine for controlling the shedding mechanism by means of twines connectable to the harness cords;
separable couplings for selectively connecting and disconnecting the twines to the harness cords, each coupling comprising a first and a second coupling element, the first coupling element being fastened to at least one of the harness cords and the second coupling element being fastened to one of the twines, the first and second coupling elements being connectable by their relative movement up to a first position so that the harness cords are connected to the twines of the Jacquard machine and are disconnectable by further movement up to a second position so that the harness cords are disconnected from the twines of the Jacquard machine;
a first plate having a number of openings, each of the harness cords being able to be passed through one of the openings;
a second plate having a number of openings, each of the twines being able to be passed through one of the openings;
the first plate and the second plate being movable relative to each other so that all separable couplings can be moved together into the first and the second position; and
the shedding mechanism, including the harness cords and the first coupling elements fastened thereto, and the first plate being disconnectable from the seam weaving machine.
Preferably, the movement by which the first and second coupling elements are connectable and disconnectable is a movement in axial direction of the first and second coupling elements.
Preferably, the first plate is a deflector plate and the second plate is a counterpressure plate, which are movable on guiding rods extending on a carriage carrying the Jacquard machine, the deflector plate being transferable onto similar guiding rods mounted on the harness carriage.
In still another aspect, the invention provides a harness carriage including means for holding the shedding mechanism, including the harness cords connected thereto and the first coupling elements fastened thereto, and the deflector plate in the same relative position as when they are connected with the seam weaving machine so that they are transferable from the seam weaving machine to the harness carriage.
Preferably, the harness carriage further includes a support for the shedding mechanism, the support including means for lowering and raising the shedding mechanism so that the harness cords can be tensioned and slackened.
Preferably, the harness carriage includes a support for storing the weft threads to be drawn in through the shedding mechanism and a support for a tensioning device for tensioning the drawn-in weft threads, the weft thread support being releasably attached to the harness carriage and the tensioning device being transferable from the seam weaving machine to the harness carriage.
New weft threads can be drawn in through the eyeletted heddles or eyelets of the shedding mechanism while the shedding mechanism is supported by the harness carriage. Another harness can in the meantime be mounted on the seam weaving machine so that the operation of the seam weaving machine does not have to be interrupted or stopped while new weft threads are drawn in.